Marine engine lubrication

A method of preparing an additive concentrate for a marine engine lubricating oil composition having both viscosity stability at 60° C. and rust inhibitory characteristics:

• (i) comprising the steps of providing as separate additive components:
• (A) at least one overbased metal detergent;
• and
• (B) an oil-soluble alkoxylated alcohol, having an HLB in the range 7-9.5, represented by the formula R[O—(CH2)x]y—OH
• where R is a linear alkyl group having from 12 to 20 carbon atoms, x is an integer from 1 to 10, and y is an integer from 2 to 10;
• the ratio of x to y being such as to provide an HLB in the above range;
• and
• (ii) admixing an oil of lubricating viscosity in a concentrate-forming amount with additive comprising additive components (A) and (B), so as to provide a marine engine lubricating oil composition having both viscosity stability at 60° C. and rust inhibitory characteristics.